Peterson, Good to see ya back here! (Must be goundhog day since you popped up, heh?)
I use Dupli under Tamiya all the time, but once in a great while it will do some micro fish eye.
Tamiya primer is always best, and when I'm doing a contest paint job, I'll do bodywork in dupli and top it with Tamiya primer.
Never used duplicolor clear, don't really like Tamiya clear (its hot on Tamiya colors). I use Testors new lacquer clear exclusively, now. Yes, Testors Lacquer clear will work on Tamiya color. Testors is the only thing that stands up to the abuse I call polishing!